Wool is a widely used fibre particularly in the clothing industry, but limitations on the properties of wool textiles have resulted in considerable research in the past with a view to improving wool textiles, for example with respect to improving resistance to soiling, creasing and importantly shrinking. A stimulus to this research has been the market demand for 100% wool garments which are washable and need a minimum of ironing. According to the prior art, such woollen garments can only be made by combining a shrinkproofing treatment with a permanent setting treatment.
Techniques have been published for shrinkproofing wool textiles by the application of preformed polymer resins. These techniques rely on the use of catalysts and usually elevated temperatures in order to bring about insolubilisation and fixation of the resin to the wool. This is disadvantageous as well as inconvenient from a manufacturing point of view.
Typically, curing of the polymer resin under the influence of the catalyst will require temperatures in the range of 80.degree. C. to 150.degree. C., and this technique can result in significant loss of strength of the textile, considerable cost and inconvenience of having to remove residual catalyst after the curing process, the development of unpleasant odours and fumes, and contamination and corrosion of equipment.
Despite these disadvantages, the acute need for an effective shrinkproofing process for wool textiles has resulted in the commercial application of polymer treatments using thermal/catalytic curing. A range of commercial polymer resins has been developed and these resins have been used despite the inherent disadvantages and difficulties in using such resins.
To be acceptable the resin must leave the textile with the desirable feel and "hand" and in general, soft polymers with a flexible "backbone" have been preferred. Furthermore, a thin film of polymer is all that is desired on the wool fibres in order to cause only a small increase in weight of the textile and to avoid imparting stiffness.
In the prior art, the use of high temperatures for curing textile resins has been accepted as necessary in order to speed up the curing reactions by expelling volatile reaction products (e.g. water, formaldehyde, alcohols), or by inducing the desired activity in the catalysts, many of which are only "latent" catalysts which are ineffective at low (ambient) temperatures.
The applicants have investigated the question of curing resins of the type referred to above at ambient temperature using ionising radiation, but it does not appear that such polymer resins are amenable to radiation curing techniques per se. Ionizing radiation may be defined as radiation having sufficient energy to create ion pairs by displacing electrons from atoms, i.e. at least about 32 electron volts, and this includes electromagnetic radiation (X-rays and gamma-rays) and particle radiation (especially electrons).
In another prior art proposal, it has been demonstrated that certain monomers, usually of the vinyl unsaturated type, can be applied to textiles and that ionising radiation can be used to initiate chain polymerisation reactions. It is to be noted that the technical problems and characteristics of monomers are quite different from that which will be found in the technology associated with preformed polymers. Potentially such a process has the advantage of obviating the use of activating agents and catalysts which require subsequent removal. However, such monomer-polymerisation reactions have not conferred shrink-resistance, and no practical processes using such methods have been demonstrated.